This invention relates to apparatuses and methods for monitoring personnel.
In one class of personnel monitoring system, a detector is positioned near exits or in passageways to determine when a person or an object is moving through the passageway or door. At that time, a signal is transmitted to a monitoring station indicating that a person or object is going through the door. Among other uses, such systems are used as security systems to determine if unauthorized patients are leaving a nursing home or the like. One such system is disclosed in U.S. Pat. No. 4,095,214.
In some such systems, a first signal is generated when the patient enters a first region. If a second condition occurs, such as the opening of a door, an alarm signal is given. A system of this type is disclosed in U.S. Pat. No. 4,682,155. In some of the known systems, a person carries an active device such as a transmitter, and in others, the person carries a passive device which receives signals and retransmits the signals when the person is in a predetermined range of the transmitter. Still other such devices rely upon a pressure pad which may be stepped upon or a combination of a device carried by a person and a location mounted device such as a device that detects the pressure of a foot step or the opening of a door.
The prior art personnel monitoring system of this class may generate a signal when the personnel being monitored are near a passageway but do not provide an alarm or warning unless a monitored person gives further indications of trying to go through the passageway.
The prior art personnel monitoring systems have several disadvantages, such as for example: (1) they do not provide advanced warning that a monitored person may be about to go through the passageway; (2) the signals may be given at a time when the central station doing the monitoring is unattended, thus permitting the persons to proceed a substantial distance before it is detected that they have left; (3) the systems can be defeated by a careful person attempting to avoid detection until the last minute and then quickly proceed through the passageway; and (4) the systems are susceptible to failure because of a temporary malfunction because there may be inadequate warning.
Devices are known which give a plurality of different signals depending on the amount of time that an object is at a particular station. For example, some detectors utilized by drive-ins give one signal when a car is near a service window and another signal if a car remains there unserviced after a particular period of time.
While such a system could be employed to detect a person who is spending a prolonged time attempting to exit through the passageway, they have not been applied in this manner even though they have been available for a substantial number of years in other localities. Moreover, they are not adapted to merely alert personnel to wait for an actual attempt to go through the passageway but instead the second signal is provided only to indicate that someone has been waiting a long time for service.